The present invention relates to a technique for acquiring information about a focus when an earthquake occurs, and rapidly notifying earthquake announcement information such as expected time of arrival and estimated seismic intensity to various locations.
When an earthquake occurs, after the preliminary tremor (P wave, primary wave), a main shockwave (S wave, secondary wave) will occur. Although the main shockwave is generated several seconds—tens of seconds after the preliminary tremor, the damage by the earthquake is due to the large tremor of the main shockwave. For this reason, it is desirable to acquire information about the focus promptly from the preliminary tremor, and to give expected arrival data to various locations within the several seconds—several tens of seconds before the main shockwave arrives. This is because immediate steps can be taken to reduce the damage, such as extinguishing fire or hiding in a safe place under a desk, before the main shockwave arrives.
Referring to FIG. 19, we can estimate the time of arrival of the earthquake (main shockwave) from the focal depth and the distance from an object point (evaluation point) calculated from latitude/longitude, based on information about the location of the epicenter, depth and magnitude. We can also estimate and calculate the seismic intensity at the object point (evaluation point) from information about the geology of the object point, etc. By obtaining information about the focus based on the preliminary tremor, we can calculate the expected time of arrival of the earthquake and estimated seismic intensity. In recent years, a system has been provided which calculates earthquake prediction information using data such as location information and geological information, etc., for various locations when information about the focus is input.
As examples of the prior art, JP-A 2007-025962 discloses a technique which displays a time remaining until a natural disaster such as an earthquake arrives in which the plural portable information terminals receive firefighting information and Japanese Standard Time, and calculate the time remaining until the natural disaster arrives in the region. According to JP-A 2007-025962, this invention discloses a measurement terminal which detects a natural phenomenon and transmits it's information, a first data processing device which calculates a location where the natural phenomenon occurred and extracts a region which the natural phenomenon is expected to affect, and generates disaster announcement information by estimating an expected time of arrival of the natural phenomenon in the region, a second data-processing device which generates anti-disaster information for each region by classifying the disaster announcement information for each region, and transmits it, a reference radio wave station which has information showing Japan Standard Time and transmits a reference radio wave, and a portable telephone network which receives the anti-disaster information from the second data processing device, and transmits Japan Standard Time shown by the reference radio wave.
JP-A 2005-222203 discloses a technique whereby real-time earthquake information distributed by the Meteorological Agency and the like before the arrival of the main shockwave is transmitted to relevant departments at the Fire Station to reduce the damage by the earthquake. According to JP-A 2005-222203, a receiving/calculation device which can receive real-time earthquake information from the Meteorological Agency and real-time earthquake information conferences, is installed by the National Fire Prevention and Control Administration. The National Fire Prevention and Control Administration also distribute earthquake information, and this information is received by fire stations. The receiving/calculation device has a function to calculate a measured seismic intensity equivalent value and a main shockwave time of arrival, and the device installed by the National Fire Prevention and Control Administration has a simultaneous call device which issues calls to firefighting personnel. A display device, fire engines and an emergency vehicle shutter automatic open/close device are installed by the National Fire Prevention and Control Administration, as well as signaling devices for contacting anti-disaster organizations such as fire stations, city halls and regional aid teams.
According to these related art technologies, earthquake prediction information is calculated, however, it is difficult to notify the information promptly and accurately to various locations. Regarding the earthquake prediction information, it is desirable to set up as many object points as possible, and provide them with detailed information. However, the calculation load on the system becomes very large as the number of object points increases, so notification of the information may be delayed. To solve this problem, a system is desired which can calculate as accurate a value as possible while reducing the calculation load on the system.
Since there is usually only several seconds—several tens of seconds until the main shockwave arrives after a notice is issued, even if the system correctly notifies an expected time of arrival (For example, HH:MM:SS HH is hour, MM is minute SS is second) to various locations, unless a terminal which received the expected time of arrival has the correct time down to the last second, the terminal cannot know how many seconds remain before the earthquake arrives. When there is a major earthquake, the amount of communications increases, and as a result there is a communications delay. Therefore, as compared with the (x seconds remaining) calculated by the system, there is a risk that the true time remaining will have an offset due to communications delay. Hence, although the system sends information about (x seconds remaining) until arrival of the earthquake (main shockwave), there has been a technical problem in how to reproduce this accurately at the terminal which receives the notice via the communications network.
In order to solve this problem, the terminal which receives the notice calculates the time remaining and avoids communications delay. The terminal must also count the correct time down to the last second. There is a further problem how to adjust the time in case the terminal measures the time by itself. It is therefore desirable to have as many object points as possible and notify detailed earthquake information thereto without imposing an excessive load on the server and terminal calculations.